The known gas mask canisters are satisfactory in many respects, but are subject to certain manufacturing limitations. In the manufacture of the existing canisters an adsorbent material, normally charcoal, is deposited in a level bed in the bottom of a canister. Pressure is applied to the charcoal bed and a diaphragm is locked in place under pressure by rolling a groove in the canister body to keep pressure on the bed. A preformed filter for particulate materials and a top diaphragm are then placed over the charcoal bed, with an adhesive sealant around the outer edge. After four hours of exposure the adhesive is cured and a cover is mounted on the canister. The canister may then be sealed with a rubber plug pushed into the inlet opening in the cover and a screw cover fitted to the bottom outlet opening.
With this procedure, the charcoal is left exposed to ambient conditions in the assembly area for a considerable time (4 hours or more). This may lead to an excessive moisture content in the hydroscopic carbon. The assembly plant can be air conditioned to provide a very dry atmosphere, but this is expensive and causes discomfort to the workers in the area.
Other characteristics of the known canister that could be improved are resistance and damage in the prevention of air by-passing the charcoal bed by flowing down the outer wall of the canister around the bed.
The present invention is concerned with solutions to the various problems.